X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/6b5cbf740022f7f57a425d212499f156b1641d49..e89d95f1909c0972b0e854ae05f50246f4d727d6:/src/src/tls.c

diff --git a/src/src/tls.c b/src/src/tls.c
index 63d98c806..e5aabc6b4 100644
--- a/src/src/tls.c
+++ b/src/src/tls.c
@@ -3,6 +3,7 @@
 *************************************************/
 
 /* Copyright (c) University of Cambridge 1995 - 2018 */
+/* Copyright (c) The Exim Maintainers 2020 */
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* This module provides TLS (aka SSL) support for Exim. The code for OpenSSL is
@@ -61,8 +62,6 @@ static int ssl_xfer_eof = FALSE;
 static BOOL ssl_xfer_error = FALSE;
 #endif
 
-uschar *tls_channelbinding_b64 = NULL;
-
 
 /*************************************************
 *       Expand string; give error on failure     *
@@ -371,9 +370,14 @@ return FALSE;
 }
 
 
-/* Environment cleanup: The GnuTLS library spots SSLKEYLOGFILE in the envonment
-and writes a file by that name.  We might make the OpenSSL support do the same,
-in some future release.  Restrict that filename to be under the spool directory.
+/* Environment cleanup: The GnuTLS library uses SSLKEYLOGFILE in the environment
+and writes a file by that name.  Our OpenSSL code does the same, using keying
+info from the library API.
+The GnuTLS support only works if exim is run by root, not taking advantage of
+the setuid bit.
+You can use either the external environment (modulo the keep_environment config)
+or the add_environment config option for SSLKEYLOGFILE; the latter takes
+precedence.
 
 If the path is absolute, require it starts with the spooldir; otherwise delete
 the env variable.  If relative, prefix the spooldir.
@@ -394,10 +398,83 @@ if (path)
   else if (Ustrncmp(path, spool_directory, Ustrlen(spool_directory)) != 0)
     {
     DEBUG(D_tls)
-      debug_printf("removing env SSLKEYLOGFILE: not under spooldir\n");
+      debug_printf("removing env SSLKEYLOGFILE=%s: not under spooldir\n", path);
     unsetenv("SSLKEYLOGFILE");
     }
 }
+
+/*************************************************
+*       Drop privs for checking TLS config      *
+*************************************************/
+
+/* We want to validate TLS options during readconf, but do not want to be
+root when we call into the TLS library, in case of library linkage errors
+which cause segfaults; before this check, those were always done as the Exim
+runtime user and it makes sense to continue with that.
+
+Assumes:  tls_require_ciphers has been set, if it will be
+          exim_user has been set, if it will be
+          exim_group has been set, if it will be
+
+Returns:  bool for "okay"; false will cause caller to immediately exit.
+*/
+
+BOOL
+tls_dropprivs_validate_require_cipher(BOOL nowarn)
+{
+const uschar *errmsg;
+pid_t pid;
+int rc, status;
+void (*oldsignal)(int);
+
+/* If TLS will never be used, no point checking ciphers */
+
+if (  !tls_advertise_hosts
+   || !*tls_advertise_hosts
+   || Ustrcmp(tls_advertise_hosts, ":") == 0
+   )
+  return TRUE;
+else if (!nowarn && !tls_certificate)
+  log_write(0, LOG_MAIN,
+    "Warning: No server certificate defined; will use a selfsigned one.\n"
+    " Suggested action: either install a certificate or change tls_advertise_hosts option");
+
+oldsignal = signal(SIGCHLD, SIG_DFL);
+
+fflush(NULL);
+if ((pid = exim_fork(US"cipher-validate")) < 0)
+  log_write(0, LOG_MAIN|LOG_PANIC_DIE, "fork failed for TLS check");
+
+if (pid == 0)
+  {
+  /* in some modes, will have dropped privilege already */
+  if (!geteuid())
+    exim_setugid(exim_uid, exim_gid, FALSE,
+        US"calling tls_validate_require_cipher");
+
+  if ((errmsg = tls_validate_require_cipher()))
+    log_write(0, LOG_PANIC_DIE|LOG_CONFIG,
+        "tls_require_ciphers invalid: %s", errmsg);
+  fflush(NULL);
+  exim_underbar_exit(EXIT_SUCCESS);
+  }
+
+do {
+  rc = waitpid(pid, &status, 0);
+} while (rc < 0 && errno == EINTR);
+
+DEBUG(D_tls)
+  debug_printf("tls_validate_require_cipher child %d ended: status=0x%x\n",
+      (int)pid, status);
+
+signal(SIGCHLD, oldsignal);
+
+return status == 0;
+}
+
+
+
+
 #endif	/*!DISABLE_TLS*/
 #endif	/*!MACRO_PREDEF*/